Which of the choices below is one of the primary gases found in the atmosphere?

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

What is created when solids, liquids, an gases mix with one another

If a tank filled with water contains a block and the height of the water above point a within the block is 0.8 meter, what is the pressure at point a?